1. Field of the Invention
This invention pertains to sorting machines that optically sort or separate nonstandard fungible objects from standard objects as they pass a viewing station by viewing such objects in at least two different frequency spectrums and particularly to such sorting machines utilizing detector elements comprised of two or more different photo-sensitive devices.
2. Description of Prior Art
A typical sorting machine of the type utilizing the present invention can be either a gravity-fed channel sorting machine or a belt sorting machine that passes a stream of objects or products to be sorted through an optical viewing station. Typically, the stream is comprised of standard fungible agricultural products, such as coffee beans, tomatoes or the like that are known to be of a standard hue or color in at least two bands of the frequency spectrum. However, if a product is overripe, bruised, or of a different grade from standard, it will have a non-standard hue or color in at least one of the two bands for which the standard products have a known standard hue or color. Such nonstandard products can be detected and removed or ejected from the stream by optical devices positioned vis-a-vis a viewing station through which the product stream passes. A sorting machine may have a plurality of parallel channels or paths, each with its own optical viewing station. Moreover, each optical viewing station can have more than one optical sensing device. For example, it is desirable to view the products or objects from different angles so that a spot hidden from view when viewed at a first angle will not be hidden from view when viewed at a second or third angle. However, for purposes of simplicity, each channel or path product stream can be considered as a continuous movement of singulated products that pass by a simplified optical viewing station.
An optical viewing station includes one or more lights to illuminate the products in the stream. An illuminated product reflects light and other frequencies, which are sensed by properly positioned photosensitive devices for monitoring the predetermined standard frequency spectrums discussed above. When a reflection is detected as being below a predetermined threshold value in one of the predetermined standard frequency spectrums, an ejection device, such as a strategically located air jet or a mechanical ejection finger is enabled and subsequently activated when the nonstandard product is positioned opposite the ejection device.
Alternative to the above operation, the detector can be adjusted to operate the ejector when a reflection deemed to be nonstandard is above a predetermined threshold value in one of the predetermined standard frequency spectrums. In such case, standard products would be passed since their reflections would be below the threshold values.
It is common in the prior art to use multiple photo or optical detectors for each spectrum, one for each pixel or photo site in a grid of a viewing window. One such system as this is disclosed in U.S. Pat. No. 5,062,532, issued Nov. 5, 1991 in the name of George A. Zivley, which patent is commonly assigned. The RL0256K array of photodiodes made by EG&G Reticon is suggested in the '532 patent for implementing the invention therein disclosed. However, the exemplar photodiodes of this array are wide aperture linear devices used in monochromatic or one frequency spectrum sorting. The invention described in the '532 is not limited to monochromatic sorting, but it is apparent that if bichromatic sorting was involved, first and second arrays with photodiodes tuned to the respective frequency spectrums would have to be physically separated from each other, thereby complicating the ejection firing to distinguish which array was involved in a substandard product detection. Moreover, the sources of illumination of the viewing station would have to be more numerous.
U.S. Pat. No. 5,265,732, issued Nov. 30, 1993 in the name of William C. Long, which patent also is commonly assigned, utilizes a detector that permits the detection of multiple spectrums at a single location. Shown therein is a prior art scheme utilizing a beam splitter and two filters, one for each of the two frequency spectrums used in the sorting. The patent also reveals the use of narrow band lights for illuminating the products in the product stream, rather than ordinary wide band general illumination bulbs. In such scheme, either a beam splitter and appropriate filters are used with the light sources or the light sources are shown at different angles, with appropriate filters still being required. In all events, the schemes utilize many different and complex optical devices and space requirements to implement such a scheme are a prime consideration.
Therefore, it is a feature of the present invention to provide an improved photo-optical detector for use in a sorting machine having a sandwich of at least a first and second photosensitive material that pass a composite multipeak frequency spectrum with a single multipeak optical filter (or a set of multiple optical components) in front of the sandwich for passing at least two defined light frequency spectrums, one within the wide frequency sensitivity of the first photosensitive material and the other within the wide frequency sensitivity of the second photosensitive material.
It is another feature of the present invention to provide an improved photo-optical detector of the type described above in which a first photosensitive material is silicon and a second photosensitive material is germanium.
It is still another feature of the present invention to provide a sorting machine utilizing a sandwich detector of the type generally described above that also includes electronic processor means such as a microprocessor for developing a signal for each separate device of the sandwich or, alternatively, a signal when there is a selected combination of signals from the separate devices so that ejection of a nonstandard product can be made on the existence of a single device signal or one or more selected signal combinations.
It is yet another feature of the present invention to provide an improved photo-optical detector of the type generally described above utilizing a sandwich of multiple photosensitive materials.
It is still another feature of the present invention to provide a sorting machine utilizing a sandwich photo-optical detector having more than two material devices, a filter having more than two defined light frequency spectral sensitivities, and electronic processor means for selecting one or more combinations of signals from the various devices for activating an ejector to remove nonstandard products from a product stream being sorted.